The present invention relates to a safety syringe for medical and industrial applications and particularly relates to a syringe having a needle adapted for withdrawal into the barrel of the syringe after use for disposal purposes, thereby eliminating or minimizing needlestick injuries.
Needlestick injuries from syringe needles are a common and increasing problem and cause significant concern because of the potential for transmission of diseases such as AIDS and Hepatitis B. A discussion of this type of injury and a variety of solutions to avoid the injury by using a syringe having a retractable needle are discussed in U.S. Pat. No. 6,117,113, of common assignee herewith, the disclosure of which is incorporated herein by reference. Various mechanical structures are disclosed in that patent and other patents for withdrawing a needle into the barrel of the syringe after use. A number of such structures rely on an interaction between an adapter carrying the needle, the distal end of the barrel and the axially movable plunger to withdraw the needle into the syringe barrel. Particularly, in a form of syringe preferred by assignee of the present application, the adapter is releasable from the distal end of the barrel by engaging the plunger with the adapter and rotating the adapter relative to the barrel. This enables the adapter, together with the needle carried thereby, to be released from the barrel end and withdrawn into the syringe barrel as the plunger is axially withdrawn in a direction away from the distal end of the barrel. The adapter is preferably screw threaded into the barrel end, although the rotational action to release the adapter is not limited to a screw thread, e.g., a bayonet-type joint could be used.
While screw threads once torqued have substantial resistance to rotation in a direction tending to release the adapter from the barrel end, there remains the potential for inadvertent rotation of the adapter in a direction relative to the barrel end which would release the adapter from the barrel end. For example, this may occur during application of a standard Luer needle onto a Luer locking element on the adapter or barrel end. It will also be appreciated that inadvertent rotation of the adapter relative to the barrel in a direction tending to release the adapter from the barrel breaks the seal between the adapter and barrel. Accordingly, there is a need to preclude inadvertent rotation of the adapter relative to the barrel in a direction tending to release or unseal the adapter from the barrel end, while simultaneously enabling the adapter to be rotated in the same direction to intentionally release the adapter from the barrel for withdrawal with the needle into the barrel.
In accordance with a preferred embodiment of the present invention, there is provided a safety syringe having an adapter for carrying a needle and which adapter is rotationally releasable from the distal end of the barrel to enable withdrawal of the adapter, including the needle carried thereby, into the syringe barrel while precluding inadvertent rotation of the adapter relative to the barrel in the same direction to release or unseal the adapter from the barrel end. As described in the above-identified patent, the plunger carries adapter engagement structure at its distal end, while the adapter carries plunger engagement structure at its proximal end. Upon engagement of the plunger with the adapter, the plunger is rotationally self-aligned relative to the barrel and adapter, enabling drive surfaces on the adapter engagement structure of the plunger to engage driven surfaces on the plunger engagement structure of the adapter whereby the adapter can be rotationally released from the distal end of the barrel in response to joint rotation of the plunger and adapter relative to the barrel. In accordance with the present invention, however, the adapter and distal end of the barrel have interengaging elements which inhibit or preclude rotation of the adapter relative to the distal end of the barrel in a direction tending to release the adapter from the barrel end. Additionally, the engagement structures between the plunger and adapter cooperate to disable the interengaging elements and release the adapter for rotation relative to the barrel, thus enabling the adapter to be rotated relative to and to be released from the barrel end and, together with the needle, withdrawn into the barrel.
The interengaging elements between the adapter and the barrel end particularly include one or more stops carried by one of the adapter and barrel end and one or more catches carried by the other of the adapter and barrel end. In a preferred embodiment, the barrel has a plurality of circumferentially spaced splines and the adapter includes one or more catches engageable with the splines to prevent or inhibit rotation of the adapter relative to the barrel in a direction tending to release or unseal the adapter from the barrel end.
More particularly, each catch, preferably carried by the adapter, comprises a finger elastically flexible in a generally radial direction for engaging a spline on the barrel end. By engaging the spline, rotation of the adapter relative to the barrel end in a direction to release or unseal the adapter from the barrel end is precluded. To release the adapter for rotational movement relative to the barrel end, the adapter-engagement structure carried by the distal end of the plunger has surfaces which, in response to axial movement of the plunger toward the distal end of the barrel, cooperate with the fingers to displace the fingers, e.g., in a radially inward direction, from engagement with the stops. Preferably, the plunger includes a generally annular element which contacts tapered surfaces on the fingers to displace the fingers radially inwardly to release the adapter for rotation relative to the barrel end. Additionally, the element includes a radially projecting rib which engages in a radially outwardly opening slot of each finger to connect the plunger and adapter to one another. The rib and each finger and slot are configured to permit the fingers to be displaced radially inwardly from a first position preventing rotation between the barrel and the adapter, hence locking the adapter to the barrel end, into a second position. In that second position, the catches on the fingers clear the splines by a substantial margin. The rib and fingers then cooperate to permit displacement of the fingers radially outwardly into a third position in which the rib maintains the catches clear of the splines. Also, in that third position with the ribs engaging in the slots of the fingers, the adapter and plunger are connected one to the other for joint axial movement. Consequently, after the interengaging elements are disabled and upon joint rotation of the plunger and adapter relative to the barrel, the adapter is rotated into a position releasing it from the barrel end thereby, enabling the adapter and needle carried thereby to be withdrawn into the barrel upon joint axial withdrawing movement of the plunger and adapter.
In a preferred embodiment according to the present invention, there is provided a syringe comprising an axially elongated barrel having a hollow interior, an adapter carried by the barrel adjacent a distal end thereof and releasable therefrom in response to rotation relative to and about the axis of the barrel, the adapter having a passage for providing fluid communication with the interior of the barrel, a plunger axially movable in the barrel between positions axially spaced from the adapter and engaging the adapter, adapter-engagement structure disposed adjacent a first end of the plunger and engageable with plunger engagement structure on the adapter for enabling rotation of the adapter relative to the barrel in response to relative rotation of the plunger and barrel to cause the adapter to part from the distal end of the barrel, the structures having engageable surfaces enabling withdrawal of the adapter, when parted from the distal end of the barrel, into the interior of the barrel upon joint axial movement of the plunger and the adapter in a direction away from the distal end of the barrel and a stop carried by one of the adapter and the distal end of the barrel and a catch carried by another of the adapter and the distal end of the barrel engageable with the stop in a first position thereof to at least inhibit relative rotational movement of the adapter and the distal end of the barrel in a direction tending to cause the adapter to part from the distal end of the barrel, the catch being movable to a second position to release the adapter and the distal end of the barrel for relative rotational movement enabling the adapter to part from the distal end of the barrel in response to relative rotation of the adapter and the barrel.
In a further preferred embodiment according to the present invention, there is provided a syringe comprising an axially elongated barrel having a hollow interior, an adapter carried by the barrel adjacent a distal end thereof and removable therefrom in response to rotation relative to and about the axis of the barrel, the adapter having a passage for providing fluid communication with the interior of the barrel, a plunger axially movable in the barrel between positions axially spaced from the adapter and engaging the adapter, an adapter-engagement structure disposed adjacent a first end of the plunger and engageable with mating engagement structure on the adapter for enabling rotation of the adapter and distal end of the barrel relative to one another to cause the adapter to part from the distal end of the barrel, means cooperable between the adapter and the barrel for preventing relative rotation of the adapter and the distal end of the barrel, connective surfaces engageable between the plunger and adapter enabling withdrawal of the adapter, when parted from the distal end of the barrel, into the interior of the barrel upon joint axial movement of the plunger and the adapter in a direction away from the distal end of the barrel and means cooperable between the plunger and the adapter for disabling the preventing means thereby enabling relative rotation of the adapter and the distal end of the barrel and withdrawal of the adapter, when parted from the distal end of the barrel, into the interior of the barrel.